Filtering particulate materials in continuous emission monitoring systems

Abstract

A filtering system for monitoring fluid emissions from a process includes a plurality of filter assembly sections arranged in a parallel fluid flow manner with respect to each other so as to selectively receive a sample fluid (e.g., a sample gas) entering at an inlet of the system. Each filter assembly section includes a filter unit to filter particulate materials from a fluid flowing through the filter, first and second valves disposed at upstream and downstream locations of the filter unit, and a blowback flow path configured to selectively direct a cleaning fluid through the filter unit in a direction that opposes a direction in which the sample fluid flows through the filter unit. Each filter assembly section can be selectively isolated from other portions of the system so as to prevent the sample fluid from flowing through the filter assembly section while allowing a cleaning fluid to be delivered through the blowback flow path of the filter assembly section.

1. A method of monitoring fluid emissions from processing equipment, the method comprising:
 extracting a sample fluid from the processing equipment; 
 delivering the sample fluid to a filter assembly comprising a plurality of filter assembly sections arranged in a parallel fluid flow manner with respect to each other, wherein each filter assembly section includes a filter unit and first and second valves disposed at upstream and downstream locations of the filter unit to isolate each filter assembly section from other portions of the filter assembly; 
 selectively controlling the flow of the sample fluid through at least a first filter assembly section by opening the first and second valves of the first filter assembly section while preventing the sample fluid from flowing through at least a second filter assembly section by maintaining the first and second valves of the second filter assembly section in a closed position, wherein the filter unit of the first filter assembly section filters particulate materials from the sample fluid flowing through the first filter assembly section; 
 delivering the filtered sample fluid from the filter assembly to an analyzer section that includes at least one analyzer to determine the concentration of at least one species within the filtered sample fluid; 
 switching the flow of sample gas from the first filter assembly section to the second filter assembly section by closing the first and second valves of the first filter assembly section and opening the first and second valves of the second filter assembly section; and 
 directing a filter cleaning fluid through the filter unit of the first filter assembly section in a direction that opposes a direction in which the sample fluid flows through the filter unit of the first filter assembly section. 
 
   
   
     2. The method of  claim 1 , wherein the sample fluid comprises a sample gas. 
   
   
     3. The method of  claim 2 , wherein the at least one analyzer of the analyzer section determines the concentration of at least one of CO, CO 2 , NO x , O 2  and H 2  in the sample gas. 
   
   
     4. The method of  claim 1 , wherein the flow of sample gas is switched from the first filter assembly section to the second filter assembly section when the flow rate of sample gas through the first filter assembly section drops below a threshold value. 
   
   
     5. The method of  claim 1 , wherein the flow of sample gas is switched from the first filter assembly section to the second filter assembly section is automatically switched via a controller. 
   
   
     6. The method of  claim 1 , wherein the filter unit of the first filter assembly section includes a hollow outer housing and a hollow inner filter member disposed within the outer housing, the filter unit is arranged within the first filter assembly section such that sample gas flowing through the first filter assembly section flows into an inlet of the outer housing, through portions of the inner filter member and out of an outlet of the inner filter member. 
   
   
     7. The method of  claim 6 , wherein the inner filter member comprises at least one of a sintered metal material and a sintered ceramic material. 
   
   
     8. The method of  claim 6 , wherein the directing of the filter cleaning fluid through the filter unit of the first filter assembly section comprises:
 delivering the filter cleaning fluid from a first fluid line directly into the outlet of the inner filter member and directly into the outer housing; and 
 delivering the filter cleaning fluid from the inlet of the outer housing to a second fluid line so as to remove the filter cleaning fluid from the first filter assembly section. 
 
   
   
     9. The method of  claim 2 , wherein the sample gas is extracted from the processing equipment via a sample probe that is configured to operate in temperature range up to about 1500° C. 
   
   
     10. The method of  claim 9 , wherein the processing equipment from which the sample gas is extracted comprises an electric arc furnace. 
   
   
     11. The method of  claim 2 , further comprising:
 removing water from the filtered sample gas prior to delivery of the filtered sample gas to the analyzer section.